This invention concerns a device and method capable of providing high density information storage. It is related to a series of commonly assigned patents using charge transfer complexes in information storage technology. These are incorporated by reference and are as follows:
U.S. Pat. No. 4,371,883--Current Controlled Bistable Electrical Organic Thin Film Switching Device;
U.S. Pat. No. 4,507,672--Method of Fabricating a Current Controlled Bistable Electrical Organic Thin Film Switching Device;
U.S. Pat. No. 4,574,366--Optical Storage and Switching Devices Using Organic Charge Transfer Salts;
U.S. Pat. No. 4,652,894--An Electrical Organic Thin Film Switching Device Switching Between Detectably Different Oxidation States;
U.S. Pat. No. 4,663,270--Multistate Optical Switching and Memory Using an Amphoteric Organic Charge Transfer Material;
U.S. Pat. No. 4,684,598--An Enhanced Optical Sensitive Medium Using Organic Charge Transfer Materials to Provide Reproducible Thermal/Optical Erasure; and
U.S. Pat. No. 4,731,756--Optical Storage and Switching Devices Using Organic Charge Transfer Salts (Cont.).
All of these patents are based on the electron transfer mechanism of charge transfer complexes, in particular the Metaltetracyanoquinodimethane (TCNQ) complexes.
U.S. Pat. No. 4,885,368, invented by Siefried Huenig, et al, corresponds to German patent DE 3522232 entitled "Radical Ion Salts". This reference describes N,N'-dicyanoquinonediimines (DCNQI) compositions similar to those used in the present invention.
Siegfried Huenig is also the author of a scientific paper entitled "Aromatic/Quinoid Systems: Principles and Applications", Pure & Appl. Chem., Vol. 62, No. 3, pp. 395-406, 1990. In this paper, the abstract and section 5 discuss DCNQI compositions. However, these relate charge transfer activities in solution and not in a solid film.
A scientific paper entitled "An Optical Phase Transition in Thin Films of Highly Conducting Charge-Transfer Salts: silver and copper, 2,5-dimethyl-N,N'-dicyanoquinonediimine", Synthetic Metals, published Aug. 14, 1991 describes work performed by the three inventors of the present invention, Yamaguchi, Viands and Potember.
In U.S. Pat. No. 4,916,688 entitled "Data Storage Method Using State Transformable Materials", scanning tunneling microscopy is used to selectively melt discrete areas of a state transformable film. This is an amorphous-to-crystalline phase transformation. The thin film is a metal/metal compound material as opposed to a nonstochiometric alloy.